That's a great question! Figuring out the right size bag liner can be frustrating, but it's actually quite simple once you know what to measure. Here's a quick and easy method.
First, grab a tape measure. You'll need two key dimensions: height and width/diameter.
1. For Height: Measure from the *bottom* of the bin's interior straight up to just under the rim. Don't measure the outside. Add 4-6 inches (10-15 cm) to this number. This extra length gives you enough bag to fold over the rim, which is crucial for keeping it secure and neat.
2. For Width: If your bin is rectangular, measure the length and width of the interior bottom. If it's round, measure the diameter (the distance across the center). The bag's listed "width" or "capacity" (like 13 gallons) should correspond to these measurements.
A handy tip: Check your current box of bags. Most list dimensions or a gallon/liter capacity. Match your bin's measurements to those specs. When in doubt, if your bin is a standard 13-gallon kitchen size, a 13-gallon bag is your safe bet. For taller, slim urban bins, you might need a "tall" variant.
The goal is a liner that sits snugly at the bottom, stretches up the sides, and has enough material to cuff neatly over the top—preventing it from slipping in. A perfectly fitted liner makes cleanup so much easier!